Household electric washing machine is divided into impeller type washing machine, roller washing machine and agitator washing machine, wherein, roller washing machine was first applied in Europe. With the changes of people's consumption level and concept, roller washing machine has been more and more widely accepted by Asian people. In the meantime, with the continuous improvement of social living environment and family life quality of washing machine users, quiet living environment has attracted more and more public attention. Furthermore, household appliance noise has also become one of the important issues to be solved by each manufacturer, in which, silent index of washing machine has been raised increasingly.
Roller washing machine adopts upper-drainage method, and the water in the tub is discharged to the outside via draining pump and draining pipe. During draining, the buzz noise generated from the water flow impact inside the water pipe on draining pump can't be settled thoroughly. After the water in the roller washing machine is drained, due to a 1.2 m lift in the drain pump, the water stored in this section of water pipe can't be discharged, instead, it impacts the impeller of draining pump under the gravity. Then the water stored in this section of water pipe is tossed out by the impeller, thereby causing the buzz noise. The existing low-end washing machine is adopted with a water level sensor, and the draining pump device runs only during the whole spinning process. Even the high-end washing machine is adopted with a water level sensor, though it can judge the lowest water level at low water level and stop the operating of the draining pump, the signal of the sensor may drift under disturbance. Thus causes misjudgment easily. As a result, there still exists noise or incomplete drainage, which cannot meet the low-noise requirement of users.
The Chinese Patent Application No. CN200920230820.4 discloses a low-noise pump shell of the draining pump for washing machine, which mainly comprises an anti-explosion hole on end face of the inner wall of the pump between the pump chamber near to the water outlet on the pump shell and filter chamber. But this anti-explosion hole is lower than the water outlet, i.e. air-water mixture forms in the pump chamber. It is unable to solve that the noise is generated in the backflow impact of the water inside the drain pipe on the impeller.
In view of that, the invention is provided.